Flow-through shutter for oven door window

ABSTRACT

A door construction having a transparent sealed window for use with a high temperature self-cleaning oven. The door includes a plurality of glass panes and a cooling air channel extending between two adjacent glass panes, and a hollow radiation blocking shutter which slides into either a lower hidden position or an upper exposed position blocking the window. The shutter in its exposed position covers over the faces of the adjacent glass panes and forces the cooling air to pass upwardly through the shutter to protect the panes from airborne particles of soil that might otherwise lodge on the glass and obscure the visibility through the window.

14s] Sept. 25, 1973 United States Patent 1191 White FLOW-THROUGH SHUTTER FOR OVEN Primary Examiner-Carroll B. Dority, Jr.

'Assistant Examiner-Larry I. Schwartz Attorney-Richard L. Caslin et al.

DOOR WINDOW [75] Inventor:

James A. White, Louisville, Ky.

[57] ABSTRACT A door-construction having a transparent sealed win- I dow for use with a high temperature self-cleaning oven.

[73] Assignee: General Electric Company,

Louisville, Ky.

[22] Filed: Sept. 5, 1972 PP N08 286,297 The door includes a plurality of glass panes and a cooling air channel extending between two adjacent glass 52 us. 126/198, 126/200 Panesand a radium bmking shutter which [51] 1 slides into either a lower hidden position or an upper exposed position blocking the window. The shutter in [58] Field of Search............................. 126/198 200 its exposed position covers over the faces of the adja- [56] References Cited cent glass panes and forces the cooling air to pass up- UNITED STATES PATENTS wardly through the shutter to protect the panes from airborne particles of soil that might otherwise lodge on the glass and obscure the visibility through the window.

10 Claims, 4 Drawing Figures FLOW-THROUGH SHUTTER FOR OVEN DOOR WINDOW BACKGROUND OF THE INVENTION A pyrolytic self-cleaning oven operates at oven temperatures as high as 950 F. as is described in the basic patent of Bohdan Hurko U.S. Pat. No. 3,121,158, which is assigned to the same-assignee as is the present invention. Windows have been available in conventional oven doors for many years. Range users have become accustomed to the convenience 'of being able to observe the food through the oven door window while the food is being cooked so as to avoid the necessity of opening the oven door, and losing some of the oven heat, in order to judge the degree of doneness of the food. Special window designs are necessary for oven doors of pyrolytic self-cleaning ovens such as the use of a movable radiation blocking shield or shutter which is positioned to close the window during the self-cleaning cycle'as is taught in the patent of Howard Baughmann and Kermit Keeling, Sr. U.S. Pat. No. 3,311,106. The main advantages of such radiation blocking shutter are that it reduces the heat loss through the window passage and thereby lowers the external surface temperatures of the door, as well as maintains-a high temperature on the internal surface of the innermost glass pane during the self-cleaning cycle so as to insure the complete removal of all food soil from the inner pane by the pyrolytic process. Safety regulations of Underwriters Laboratories, Inc. are becoming more strict each year regarding the allowable surface temperatures on the outer surface of the oven door during the self-cleaning operation. Therefore, it is incumbent upon range manufacturers to continuously refine and improve their designs to satisfy the needs of the range user.

A principle object of the present invention is to provide an oven door with a window having a movable radiation blocking shutter that also serves as a cover means for the adjacent glass panes to prevent the deposition of soil on the panes due to foreign particles pres ent in cooling air that is allowed to flow by convection through the door during a high temperature selfcleaning oven cycle.

A further object of the present invention is to provide a windowed oven door with a movable hollow shutter within a cooling air channel formed in the door such that when the shutter is in its exposed position blocking the window opening the cooling air will be forced to pass through the shutter and will not sweep the faces of the adjacent glass panes.

A further object of the present invention is to provide a windowed oven door of the class described with a resilient sealing means carried by the shutter such that when the shutter is in its hidden position it will act to close off the convection air currents through the door, again tending the prevent soil from becoming lodged on the faces of the glass panes from foreign particles present in the air.

SUMMARY OF THE INVENTION The present invention, in accordance with one form thereof, relates to an insulated door construction for use with a high-temperature oven where the door has an outer panel and an inner door liner with substantially aligned window openings in said panel and door liner, and glass panes closing said window openings. The door includes a cooling air channel between two the glass pane for both restricting the radiation of heat through the window openings and forcing the cooling air to pass through the shutter rather than sweeping across the faces of the glass pane to prevent the deposition of soil thereon.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be better understood from the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. 1 is a front elevational view of a freestanding domesticrange having a lower oven with a front-access door and a window opening embodying the present invention.

FIG. 2 is a cross sectional side elevational view on an enlarged scale taken down through the center of the door on the line 22 of FIG. 1 and showing the internal nature of the oven door with its window construction and a hollow shutter located within the cooling air channel but in its lower or hidden position for viewing within the oven cavity.

FIG. 3 is a fragmentary cross sectional plan view through one half of the oven door taken on the line 3-3 of FIG. 2 showing the hollow shutter still in its lowered position and the nature of the guide rails on the sides of the shutter for supporting the shutter for its vertical movement, as well as the partition that divides the cooling air channel into one large central window section and two smaller side channels.

FIG. 4 is a fragmentary cross sectional elevational view similar to the top portion of the door of FIG. 2 but showing the hollow shutter in its raised position where it is exposed in the window opening and covers the faces of the adjacent glass panes thereby preventing airborne soil from sweeping the faces of the panes. 7

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to consideration of the drawings and in particular to FIG. 1 there is shown for illustrative purposes a free-standing domestic range 10 having a top cooking surface 11 with a plurality of surface heating elements 12, a baking oven 14 beneath the cooktop formed by a box-like oven liner (not shown) and a front-opening drop door 16. While the oven door of the present invention is shown as being installed on an electric range it will readily be apparent to these skilled in this art that the invention is not limited to use with an electric oven as it could just as well be a gas-fired oven. A backsplash 18 rises from the cooktop 11 along the back edge thereof and it contains the necessary control components 20 which are only illustrated diagrammatically since they do not form part of the present invention.

The oven door 16, as seen in front view, is a generally rectangular and nearly square structure which is adapted to be hinged along its bottom edge to the range body. It is provided with an elongated handle 22 near its top edge so that the door may be opened and closed with ease. The door includes a rectangular window 24 3 that is of reduced size as compared with the overall size of the door, and it is located generally in the top half of the door structure.

As is best seen in FIG. 2, the oven door 16 is of generally sheet metal fabricated construction having three main elements; an outer door panel 26, an inner door liner 28 and a floating inner panel 30. In effect the inner panel 30 is part of the inner door liner 28 except that it is separated therefrom by a high temperature gasket 32 such as woven fiber glass or the like which is sandwiched between the two members to serve as a thermal break, as well as a resilient sealing means in the door gap between the door 16 and a front flange 34 of the box-like oven liner 36. The outer door panel 26 is of shallow pan shape by virtue of the fact that it has a slight rearwardly turned peripheral flange 38. The inner door liner 28 is also of shallow pan shape, and it is of mating construction with the outer door panel 26 by virtue of the fact that it has a slight front turned peripheral flange 40 which telescopes within the flange 38 of the outer door panel.

The inner door liner 28 includes a generally rectangular, central, plug like outward embossment 42 of such size as to fit closely within the front opening 44 of the front frame of the oven body. The floating inner panel 30 is likewise of shallow pan. shape having a slight front turned peripheral flange 46. The door gasket 32 is confined under the edge of the flange 46 and it extends almost entirelyaround the periphery of the panel 30 although it is not designed to have a butt joint. The free ends of the gasket are usually stopped short of each other to create a controlled air gap for the admission of a slight amount of air into the oven cavity during the self-cleaning cycle. For a better understanding of the nature of a conventional door gasket reference may be made to the patent of Clarence Getman, US. Pat. No. 3, l 89,020, which is also assigned to the assignee of the present invention. The floating inner panel 30 is provided with widely spaced brackets 47 so that fastening screws 48 may extend through the inner door liner 28 and into the brackets for holding the floating inner liner attached to the inner door liner with 'a slight amount of relative movement possible therebetween due to thermal expansion and-contraction of the members. For purposes of this application the term inner door liner as used for the remainder of the application will cover both the inner door liner 28 and the floating inner panel 30.

The outer door panel 26 is fastened to the inner door liner 28 by means of several widely spaced vertical tabs 50 which are formed along the bottom run of the flange 38 of the outer door panel. These tabs are adapted to slip into mating holes 52 in the lower run of the flange 40 of the inner door panel 28 so that this simple connection holds the bottom portion of the door together. The top portion of the door is held together by fastening screws (not shown) that extend through the inner door liner 28 into suitable brackets (not shown) on the inner surface of the outer door panel 26 as is conventional in this art.

The outer door panel 26 is furnished with a window therethrough. Notice the small window gasket 67. While three glass panes are shown, it is clear that a double window pack might also be acceptable, and that under some circumstances as many as four glass panes might be assembled together in the inner door liner 28. These three glass panes 64, 65 and 66 are joined in a subassembly by means of peripheral spacers 68 and 69 which separate the panes as well as provide a sealing means such that there'are dead air spaces 70 and 72 between the three glass panes. This subassembly is clamped together by means of an outer channel frame 74'that encircles the periphery of the three panes and prevents them from being separated. While an integral window subassembly is shown it will readily be apparent that individual mounting means for each of the glass panes could be provided. The advantage of the window subassembly is that it insures cleanliness and reduction of danger of breakage of the glass in handling during the assembly operations of the door, as well as maintains the integrity of the window sealing means to prevent vapors and grease from entering the interior of the subassembly and soiling the glass.

A sheet metal insulation guard 76 is fastened to the inside of the inner door liner 28 by fastening screws (not shown). This insulation guard has a window opening 78 in which is positioned the second glass pane 64. The interior of the floating inner panel 30 is substantially filled with thermal insulation 80 such as fiber glass or the like, and a similar blanket of insulation 82 fills the inner door liner 26 up to the insulation guard 76. This leaves an empty compartment 86 in the door near the front portion thereof that extends from bottom to top thereof and from the inner surface of the outer door panel 26 to the insulation guard 76. This hollow compartment 86 is employed as a cooling air channel by forming air inlet openigns 88, in the form of a series of elongated slots, in the bottom run of the flange 38 of the outer door panel as well as air outlet openings 90 of similar elongated slot configuration in the upper run of the flange 38 so that convection air currents of room air may pass freely up through the cooling channel 86.

As mentioned previously, a radiation blocking shield or shutter-is necessary for the window of a self-cleaning oven door where the inner oven wall temperatures may reach as high as 950 F. Such a shutter is located within the cooling air channel 86 in the present invention. One of its principle features is the fact that it is a hollow member at least from top to bottom to allow cooling air to pass up through the shutter such that the cooling air not only cools the outer door panel 26 but it also cools the shutter 95. This shutter 95 is formed by a pair of spaced metal plates 97 and 98 which are separated by small nylon slides 100 adjacent each corner thereof for mating engagement with a vertically arranged Z-shaped guide rail 102 so that the shutter may be moved in a vertical plane on the guide rails. As seen in FIG. 3 the top portion of the shutter 95 is provided with a pair of oppositely directed handles 104 which extend outwardly from the door through suitable vertically elongated slots 106 in the sides of the embossment 42 of the inner door liner 28 such that the oven door 16 must be opened before the shutter handles 104 may be reached for changing the position of the shutter. At least one simple clip member (not shown) is mounted within the door structure to engage one of the shutter handles 104 when the shutter is in its extreme raised position of FIG. 4 so that the clip member will serve as a temporary support means for the shutter against the weight of gravity which might otherwise cause the shutter to drop to its lower position when the handles are released and the door closed.

An important feature of the present invention is that the metal plates 97 and 98 of the hollow shutter 95 are so spaced that when the shutter is in itsraised or exposed position blocking the window opening the two plates 97 and 98 of the shutter closelyoverlie or cover the two adjacent glass panes 58 and 64 as is best seen in FIG. 3 to prevent airborne particles in the cooling air from sweeping the faces of these two glass panes 58 and 64 during the self-cleaning oven cylce and at the same time force substantially all of the cooling air up through the center of the hollow shutter.

It is well to provide means cooperating with the shutter 95 for sealing the air inlet openings'88 when the shutter is in its lower hidden position away from the glass panes 58 and 64. One reason for this is that this oven might be the upper oven of a combination double oven built-in appliance, and open door broiling might take place in the lower oven which would cause a large amount of grease and vapors to rise upwardly and perhaps enter the air cooling channel 86 when the shutter is in the lower position shown in FIG. 2 exposing the glass panes 58 and 64 to the likelihood that soil, will become deposited on the opposing surfaces of the panes 58 and 64. As best seen in FIG. 2, a resilient sealing means 110 in the form of an elongated strip of foam rubber is fastened to the lower portion of the shutter 95 by means of a slightly resilient, elongated angular metal plate 1 13 which is attached to the lower portion of the shutter and is of a length substantially equal to the width of the shutter. Thus, when the shutter is raised the sealing means 110 is raised and the air inlet openings 88 are free to receive cooling air, and when the shutter is lowered the foam rubber seal 110 is pressed over the elongated slots 88 and substantially seals these air openings against the passage of air therethrough. This plate 113 and seal 110 is left off the plan view of the shutter 95 in FIG. 3 to dramatize the hollow nature of the shutter 95 by seeing the slots 88 therethrough.

As best seen in the cross sectional plan view of FIG.

3, the oven door 16 is provided with conventional hinge means 115 adjacent each side of the door and they would be mounted near the bottom corner thereof. This particular door shown happens to be a removable oven door having an integral bracket member 117 for receiving a tubular like member 119 which is pivotally connected to a hinge arm 121, as by means of hinge pin 123. The hinge arm is fastened at its opposite end 125 to a fixed bracket 127 within the front frame of the oven body. For a better understanding of the complete hinge system reference may be made to an acceptable hinge system as is taught in the patent of Kermit Keeling, Sr., U.S. Pat. No. 3,600,335, which is also assigned to the same assignee as is the present invention.

It is believed sufficient to explain that the hinge means 1 requires relatively large slots or air openings in the door such that it is most difficult to seal these openings against air movement therein in a similar manner to the seal 110 closing the air inlet openings 88 in the outer door panel 26. For this reason each guide rail 102 is provided with a transverse extension or panition 130 which serves to sub-divide the air cooling channel 86into three sections, namely, a main window section located between the two partitions 130, 130,

and two side channels 132, 132 (only one of which is shown) which is located between the partition 130 and the adjacent side of the door. These partitions 130, 130 serve to restrict the air movement in the side air channels 132, 132 so that cooling air therein does not bypass the partition 130 and possibly sweep between the hollow shutter 95 and the adjacent'surface of the glass panes 58 and 64.

Having described above my invention of a novel oven door window construction for a high temperature selfcleaning oven, it will readily be apparent to those skilled in this art that certainelements of the oven design have been omitted for the sake of simplicity as they do not form part of the present invention, although they are necessary elements in the overall oven design.

Such elements are the oven door latch system and the interlock system that cooperates with the movable I shutter to sense the position of the shutter in its closed or exposed position before the oven is allowed to begin its self-cleaning cycle. For a more complete description of these missing elements attention may be given to the before-mentioned U.S. Pat. No. 3,311,106.

Modifications of this invention will occur to those skilled in this art, therefore, it is to be understood that this invention is not limited to the particular embodiments disclosed but that it is intended to cover all modifications and their equivalents which are within the .true spirit and scope of this invention as claimed.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:

1. An oven door comprising an outer panel and an inner door liner spaced inwardly therefrom, substantially aligned window openings in said panel and door liner and glass panes closing said window openings, the door including a cooling air channel between said glass panes with air inlet means along the bottom portion of the door and air outlet means along the top portion of the door, a manually operable hollow shutter, means mounting said shutter for movement within the said air channel between an open position .hidden within the door to permit viewing through said window openings and a closed position covering the glass panes for both restricting the radiation of heat through said window openings and forcing the cooling air to pass through the shutter rather than sweeping across the faces of the glass panes so as to prevent the deposition of airborne soil thereon.

2. An oven door as recited in claim 1 with sealing means carried by the lower portion of the hollow shutter so that when the shutter is in its open position the said sealing means acts to close the air inlet means to substantially prevent air movement through the said air channel.

3. An oven door of hollow sheet metal construction provided with a transparent window formed by a plurality of glass sheets mounted therein, a cooling air channel formed in the door and extending between two of the adjacent glass sheets, there being air inlet means adjacent the bottom portion of the door and air outlet means adjacent the top portion of the door, a manually operable hollow shutter, means mounting said shutter within the air channel for movement between an open hidden position within the door and a closed visible position blocking the window to restrict the radiation of heat energy through the window, and sealing means operable to close the air inlet means when the shutter is in its open position, the hollow shutter tending to protect the adjacent glass sheets from air movement when the shutter is in its closed position by causing the cooling air to by-pass the glass sheets and pass upwardly through the hollow shutter so as to prevent the deposition of airborne soil on the glass sheets which might otherwise restrict visibility through the window.

4. An oven door as recited in claim 3 wherein the said hollow shutter comprises a pair of spaced metal plates so that the shutter is substantially open at the bottom and top thereof, the said sealing means being carried by the bottom portion of the shutter and comprising resilient means for engaging and closing the air inlet means.

5. A door construction for a high temperature oven having an oven cavity formed by a box-like oven liner and a front-opening access door; the invention comprising a door having an outer door panel with a first window opening, a first glass pane covering said first window opening, an inner door liner attached to and spaced inwardly from said outer door panel, a second window opening formed in said inner door liner, at least two spaced glass panes covering said second window opening, a cooling air channel located within the door behind the first glass pane, a movable shutter, means supporting said shutter within the air channel in either a hidden position within the door for normal cooking operations or in an exposed position behind the first glass pane during a high temperature operation so as to restrict the radiation of heat energy through the window, the air channel having air inlet openings adjacent the bottom portion of the door and air outlet openings adjacent the top portion of the door, the shutter being formed of spaced panels to form a hollow construction that is open at least at the top and bottom to allow cooling air to flow therethrough, the spaced panels of the shutter covering the adjacent glass panes when the shutter is in its exposed position whereby the air flow passes through the shutter during the high temperature operation rather than sweeping across the glass panes.

6. A door construction as recited in claim 5 including vertical guide rails within the air channel on each side of the window opening, the sides of the shutter being provided with slide means engageable with the guide rails, and handle means for raising and lowering the shutter on the guide rails, and means for supporting the shutter in its raised position.

7. A door construction as recited in claim 6 with sealing means carried by the lower portion of the shutter so that when the shutter is in its lowered position the said sealing means acts to close the air inlet openings to substantially prevent air movement through the air channel, the door being provided with hinge means adjacent the two bottom comers thereof whereby air is allowed to enter the air channel in these hinge areas, the said guide rails including partition means to close off the opposite sides of the air channel into side compartments so that the air entering the door around the hinge areas does not reach the shutter and the area between the shutter and the adjacent panes of glass.

8. An oven door comprising an outer panel and an inner door liner spaced inwardly therefrom, substantially aligned window openings in said outer panel and inner liner, and spaced glass panes closing said window openings, a cooling air channel within the door that extends between two adjacent glass panes and has air inlet openings in the lower portion of the door and air outlet openings in the upper portion of the door, and a shutter mounted in the=. air channel and means for moving said shutter into either a lower hidden position or an upper exposed position between the two said adjacent glass panes, the shutter being formed of spaced panels to be hollow so that when the shutter is raised the spaced panels cover the adjacent glass panes and any upward air movement passes up through the shutter rather than sweeping across the faces of the glass panes to protect the panes from being soiled by airborne particles.

9. An oven door as recited in claim 8 wherein the said air channel includes a substantially vertical guide rail at each side of the shutter, and the shutter is furnished with slide means which cooperate with the guide rails for supporting the shutter, said guide rails cooperating with partitions that subdivide the air channel into at least three separate air channels, there being a first relatively large central window section and a pair of spaced narrow side channels.

10. An oven door as recited in claim 9 with resilient sealing means carried by the lower portion of the shutter so that when the shutter is in its lower position the sealing means acts to close the air inlet openings and prevent air movement up through the central window section of the air channel. 

1. An oven door comprising an outer panel and an inner door liner spaced inwardly therefrom, substantially aligned window openings in said panel and door liner and glass panes closing said window openings, the door including a cooling air channel between said glass panes with air inlet means along the bottom portion of the door and air outlet means along the top portion of the door, a manually operable hollow shutter, means mounting said shutter for movement within the said air channel between an open position hidden within the door to permit viewing through said window openings and a closed position covering the glass panes for both restricting the radiation of heat through said window openings and forcing the cooling air to pass through the shutter rather than sweeping across the faces of the glass panes so as to prevent the deposition of airborne soil thereon.
 2. An oven door as recited in claim 1 with sealing means carried by the lower portion of the hollow shutter so that when the shutter is in its open position the said sealing means acts to close the air inlet means to substantially prevent air movement through the said air channel.
 3. An oven door of hollow sheet metal construction provided with a transparent window formed by a plurality of glass sheets mounted therein, a cooling air channel formed in the door and extending between two of the adjacent glass sheets, there being air inlet means adjacent the bottom portion of the door and air outlet means adjacent the top portion of the door, a manually operable hollow shutter, means mounting said shutter within the air channel for movement between an open hidden position within the door and a closed visible position blocking the window to restrict the radiation of heat energy through the window, and sealing means operable to close the air inlet means when the shutter is in its open position, the hollow shutter tending to protect the adjacent glass sheets from air movement when the shutter is in its closed position by causing the cooling air to by-pass the glass sheets and pass upwardly through the hollow shutter so as to prevent the deposition of airborne soil on the glass sheets which might otherwise restrict visibility through the window.
 4. An oven door as recited in claim 3 wherein the said hollow shutter comprises a pair of spaced metal plates so that the shutter is substantially open at the bottom and top thereof, the said sealing means being carried by the bottom portion of the shutter and comprising resilient means for engaging and closing the air inlet means.
 5. A door construction for a high temperature oven having an oven cavity formed by a box-like oven liner and a front-opening access door; the invention comprising a door having an outer door panel with a first window opening, a first glass pane covering said first window opening, an inner door liner attached to and spaced inwardly from said outer door panel, a second window opening formed in said inner door liner, at least two spaced glass panes covering said second window opening, a cooling air channel located within the door behind the first glass pane, a movable shutter, means supporting said shutter within the air channel in either a hidden position within the door for normal cooking operations or in an exposed position behind the first glass pane during a high temperature operation so as to restrict the radiation of heat energy through the window, the air channel having air inlet openings adjacent the bottom portion of the door and air outlet openings adjacent the top portion of the door, the shutter being formed of spaced panels to form a hollow construction that is open at least at the top and bottom to allow cooling air to flow therethrough, the spaced panels of the shutter covering the adjacent glass panes when the shutter is in its exposed position whereby the air flow passes through the shutter during the high temperature operation rather than sweeping across the glass panes.
 6. A door construction as recited in claim 5 including vertical guide rails within the air channel on each side of the window opening, the sides of the shutter being provided with slide means engageable with the guide rails, and handle means for raising and lowering the shutter on the guide rails, and means for supporting the shutter in its raised position.
 7. A door construction as recited in claim 6 with sealing means carried by the lower portion of the shutter so that when the shutter is in its lowered position the said sealing means acts to close the air inlet openings to substantially prevent air movement through the air channel, the door being provided with hinge means adjacent the two bottom corners thereof whereby air is allowed to enter the air channel in these hinge areas, the said guide rails including partition means to close off the opposite sides of the air channel into side compartments so that the air entering the door around the hinge areas does not reach the shutter and the area between the shutter and the adjacent panes of glass.
 8. An oven door comprising an outer panel and an inner door liner spaced inwardly therefrom, substantially aligned window openings in said outer panel and inner liner, and spaced glass panes closing said window openings, a cooling air channel within the door that extends between two adjacent glass panes and has air inlet openings in the lower portion of the door and air outlet openings in the upper portion of the door, and a shutter mounted in the air channel and means for moving said shutter into either a lower hidden position or an upper exposed position between the two said adjacent glass panes, the shutter being formed of spaced panels to be hollow so that when the shutter is raised the spaced panels cover the adjacent glass panes and any upward air movement passes up through the shutter rather than sweeping across the faces of the glass panes to protect the panes from being soiled by airborne particles.
 9. An oven door as recited in claim 8 wherein the said air channel includes a substantially vertical guide rail at each side of the shutter, and the shutter is furnished with slide means which cooperate with the guide rails for supporting the shutter, said guide rails cooperating with partitions that subdivide the air channel into at least three separate air channels, there being a first relatively large central window section and a pair of spaced narrow side channels.
 10. An oven door as recited in claim 9 with resilient sealing means carried by the lower portion of the shutter so that when the shutter is in its lower position the sealing means acts to close the air inlet openings and prevent air movement up through the central window section of the air channel. 